Modified admixture suitable for soft rock cave slag concrete and preparation method thereof
By using polyfatty acid modified graphene oxide and graphene oxide composite gel in tunnel muck concrete, the problems of insufficient mechanical properties and durability of tunnel muck concrete were solved, achieving efficient concrete reinforcement and durability improvement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SICHUAN JIAOTOU CONSTR ENG CO LTD
- Filing Date
- 2026-04-22
- Publication Date
- 2026-05-19
AI Technical Summary
In existing technologies, when tunnel slag is used as concrete aggregate, its mechanical properties and durability are insufficient, making it difficult to form a strong skeleton. It is also prone to softening, which affects the long-term durability of concrete.
Polyfatty acid modified graphene oxide and graphene oxide composite gel are used as modifying admixtures. Through rapid water absorption, thickening and uniform dispersion, the density and impermeability of concrete are improved, the flexural strength is enhanced, and the intrusion of moisture and corrosive ions is blocked.
It significantly improves the density and mechanical properties of soft rock slag concrete, enhances compressive strength and impermeability, strengthens long-term durability, and realizes high-value-added resource utilization of low-quality tunnel slag.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to a modified admixture suitable for soft rock caving slag concrete and its preparation method. Background Technology
[0002] In my country's large-scale transportation infrastructure construction, tunnel projects traversing complex geological formations have become commonplace. Particularly in the mountainous regions of the southwest and northwest, railway and highway tunnels frequently pass through weathered strata, phyllite, metamorphic sandstone, mudstone, slate, and other soft rock formations. These rock masses have low strength and are easily softened by water, generating enormous amounts of tunnel debris during excavation, with the proportion of soft rock debris increasing daily. Statistics show that a single long tunnel can generate millions of cubic meters of tunnel debris, but the cost of disposing of this debris individually is high. The traditional method is to send this tunnel debris to a spoil heap, but this method not only occupies land and damages the ecological environment but may also trigger secondary disasters such as landslides and mudslides at the spoil heap.
[0003] To address the aforementioned problems, using tunnel slag as concrete aggregate is the primary way to realize its high-value resource utilization. However, tunnel slag has low strength and high crushing value, making it difficult for the prepared aggregate to form a robust skeleton in concrete, resulting in a low upper limit of concrete mechanical strength. Furthermore, the mineral composition of tunnel slag often contains a large amount of clay minerals (such as montmorillonite and illite), which are highly absorbent, easily softened, and may react adversely with cement hydration products, affecting the long-term durability of concrete. CN119461974A provides a green concrete for soft rock tunnel slag, which includes cement, tunnel slag rock-based mineral admixtures, continuously graded soft rock tunnel slag coarse aggregate, soft rock tunnel slag fine aggregate, soft rock modifier, water-reducing agent, and water. Through specific component ratios and preparation methods, it improves the mechanical properties and durability of concrete. However, its soft rock modifier cannot fundamentally enhance the internal structure of the aggregate and cannot better improve its mechanical properties.
[0004] Therefore, there is an urgent need for a modifier for soft rock caving concrete that combines mechanical properties and durability, as well as its preparation method. Summary of the Invention
[0005] The purpose of this invention is to provide a modified admixture for soft rock caving concrete and its preparation method. This modified admixture can better increase the mechanical properties and durability of soft rock caving concrete.
[0006] In a first aspect, the present invention provides a modified admixture suitable for soft rock slag concrete, the modified admixture comprising polyfatty acid modified graphene oxide and graphene oxide composite gel.
[0007] In this invention, the synergistic effect of polyfatty acid modified graphene oxide and graphene oxide composite gel enables rapid water absorption and thickening during the mixing of soft rock slag concrete, achieving rapid hardening of soft rock and significantly enhancing the density, impermeability, and flexural strength of the concrete. This is presumably because, during mixing, the graphene oxide composite gel rapidly absorbs water and swells, significantly increasing the viscosity of the paste, thereby "fixing" the soft rock aggregate and preventing water absorption and collapse, thus achieving rapid hardening. Simultaneously, the polyfatty acid modified graphene oxide is uniformly dispersed in the cement matrix, effectively filling nanoscale pores. Working in tandem with the graphene oxide composite gel in the system, it further enhances the density of the concrete, thereby improving its mechanical properties and preventing the intrusion of water and corrosive ions (such as chloride ions).
[0008] Preferably, the mass ratio of the polyfatty acid modified graphene oxide to the graphene oxide composite gel is 1:(1~10), for example 1:1, 1:3, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, and more preferably 1:(4~5).
[0009] In this invention, by controlling the ratio of polyfatty acid modified graphene oxide to graphene oxide composite gel within the above-mentioned range, internal defects in concrete can be better reduced, thereby improving the overall density and mechanical properties.
[0010] Polyfatty acid modified graphene oxide Polyfatty acid modified graphene oxide refers to a modified product formed by grafting polyfatty acid molecules onto the surface of graphene oxide. Preferably, the polyfatty acid in the polyfatty acid modified graphene oxide is selected from at least one of octadecanoic unsaturated fatty acid dimer, linoleic acid dimer, and palmitic acid dimer, with palmitic acid dimer being the most preferred.
[0011] Preferably, the preparation method of the polyfatty acid modified graphene oxide includes: (1) Graphene oxide was dispersed in N,N-dimethylformamide to obtain a graphene oxide dispersion; (2) Thionyl chloride was added dropwise to the graphene oxide dispersion for reaction, and then filtered, washed and dried to obtain the graphene oxide intermediate. (3) Polyfatty acid is dissolved in tetrahydrofuran to obtain a polyfatty acid solution, and graphene oxide intermediate is dispersed in tetrahydrofuran to obtain a graphene oxide intermediate dispersion. (4) The polyfatty acid solution was added dropwise to the graphene oxide intermediate dispersion for reflux reaction, followed by filtration, washing and drying to obtain polyfatty acid modified graphene oxide.
[0012] There are no special restrictions on the dispersion conditions in step (1) above. As long as the dispersion can be uniform, any method in the field can be used for dispersion, such as ultrasonication at 400-600W for 20-30 minutes.
[0013] Preferably, in step (1), the graphene oxide is nano-graphene oxide, and more preferably, the nano-graphene oxide has a multilayer structure, i.e., multilayer nano-graphene oxide. The multilayer nano-graphene oxide has a Dv50 particle size of 10~50 micrometers, an average number of layers of 5~10 layers, and an average thickness of 3~8 nanometers.
[0014] The multilayer nano-graphene oxide in this invention is commercially available, for example, it can be purchased from Shenzhen Liyou New Energy Technology Co., Ltd., model Graphene-510.
[0015] Preferably, in step (1), the concentration of the graphene oxide dispersion is 1~2 mg / mL.
[0016] Preferably, in step (2), the mass ratio of thionyl chloride to graphene oxide is (30~40):1.
[0017] Preferably, in step (2), the reaction conditions include: reflux reaction at 65~75°C for 12~30 hours.
[0018] Preferably, in step (2), the thionyl chloride is added over a period of 20 to 30 minutes.
[0019] There are no special restrictions on the filtration, washing and drying methods in step (2) above. For example, the material obtained after the reaction can be filtered, the filter cake can be washed with tetrahydrofuran 3 to 5 times, and then dried in a vacuum drying oven at 70 to 80°C for 8 to 24 hours.
[0020] Preferably, in step (3), the concentration of the polyfatty acid solution is 10~20 mg / mL, more preferably 15~18 mg / mL.
[0021] Preferably, in step (3), the concentration of the graphene oxide intermediate dispersion is 1~10 mg / mL, and more preferably 3~5 mg / mL.
[0022] In step (3) above, there are no special restrictions on the conditions under which polyfatty acids are dissolved in tetrahydrofuran. As long as the polyfatty acids can be dissolved in tetrahydrofuran, it is acceptable. To accelerate the dissolution efficiency, the dissolution can be carried out under heating conditions.
[0023] In step (3) above, there are no special restrictions on the dispersion conditions of the graphene oxide intermediate in tetrahydrofuran, as long as it can be dispersed evenly. For example, it can be sonicated at 400-600W for 40-60 minutes.
[0024] Preferably, in step (4), the mass ratio of the polyfatty acid in the polyfatty acid solution to the graphene oxide intermediate in the graphene oxide intermediate dispersion is (10~20):1, more preferably (12~15):1.
[0025] Preferably, in step (4), the polyfatty acid solution is dripped over a period of 20 to 30 minutes.
[0026] Preferably, in step (4), the reflux reaction conditions include: a temperature of 60~65℃ and a time of 30~40 hours.
[0027] The filtration, washing, and drying in step (4) can be conventional operating methods in the field. For example, the material obtained from the reflux reaction is filtered, the filter cake is washed with anhydrous ethanol 3 to 5 times, and finally dried in a vacuum drying oven at 40 to 50°C for 8 to 24 hours.
[0028] Specifically, the preparation methods of polyfatty acid modified graphene oxide include: (1) Graphene oxide was ultrasonically dispersed in N,N-dimethylformamide at 400-600W for 20-30 minutes to obtain a graphene oxide dispersion with a concentration of 1-2 mg / mL; (2) Add thionyl chloride dropwise (over 20-30 minutes) to the graphene oxide dispersion and reflux at 65-75°C for 12-30 hours. After the reaction, filter the material and wash the filter cake 3-5 times with tetrahydrofuran. Then dry it in a vacuum drying oven at 70-80°C for 8-24 hours to obtain the graphene oxide intermediate. The mass ratio of thionyl chloride to graphene oxide is (30-40):1. (3) Dissolve palmitic acid dimer in tetrahydrofuran to obtain a polyfatty acid solution with a concentration of 15~18 mg / mL, and disperse the graphene oxide intermediate in tetrahydrofuran under ultrasonication at 400-600W for 40~60 minutes to obtain a graphene oxide intermediate dispersion with a concentration of 3~5 mg / mL. (4) The polyfatty acid solution is added dropwise (over 20-30 minutes) to the graphene oxide intermediate dispersion and refluxed at 60-65°C for 30-40 hours. The material obtained from the reflux reaction is filtered, and the filter cake is washed 3-5 times with anhydrous ethanol. Finally, it is dried in a vacuum drying oven at 40-50°C for 8-24 hours to obtain polyfatty acid modified graphene oxide. The mass ratio of palmitic acid dimer acid in the polyfatty acid solution to graphene oxide intermediate in the graphene oxide intermediate dispersion is (12-15):1.
[0029] Graphene oxide composite gel Preferably, the modified segments in the graphene oxide composite gel include acrylamide segments, p-styrene sulfonic acid segments, and N,N'-bis(acryloyl)cystamine segments.
[0030] In this invention, the acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine segments in the graphene oxide composite gel can form a cross-linked polymer network with dynamic properties. On the one hand, the cross-linked polymer network forms hard microparticles after drying, effectively filling pores; on the other hand, it can moderately swell when exposed to water, blocking water seepage channels, thereby improving the mechanical properties of the prepared concrete.
[0031] Preferably, the molar ratio of the acrylamide segment, the p-styrene sulfonic acid segment, and the N,N'-bis(acryloyl)cysteine segment is 1:(0.5~0.8):(0.15~0.3), more preferably 1:(0.65~0.7):(0.2~0.25).
[0032] Furthermore, this invention has found that controlling the molar ratio of acrylamide segments, p-styrene sulfonic acid segments, and N,N'-bis(acryloyl)cysteine segments within the aforementioned range allows the modified admixture to better ensure the durability and density of concrete during long-term use. This is presumably because the moderate and controllable hydrophilicity of the graphene oxide composite gel within the above-mentioned ratio range enables the modified admixture to effectively disperse and retain moisture during concrete mixing, preventing microcracks caused by premature local water loss, thereby better improving density. Simultaneously, its excellent strength and toughness dynamic network further enhances density and durability. In this invention, it is understood that the acrylamide segment is provided by acrylamide, the p-styrene sulfonic acid segment is provided by p-styrene sulfonic acid, and the N,N'-bis(acryloyl)cysteine segment is provided by N,N'-bis(acryloyl)cysteine; that is, the amount of each segment corresponds to the amount of the corresponding raw material. Preferably, the preparation method of the graphene oxide composite gel includes: dispersing graphene oxide in water to prepare a graphene oxide dispersion, then adding acrylamide and p-styrene sulfonic acid for a first reaction, then adjusting the pH of the system to 7-8 using sodium hydroxide aqueous solution, then sequentially adding N,N'-bis(acryloyl)cysteine and an initiator for a second reaction, and finally performing a gelation reaction, drying, and pulverizing to obtain the graphene oxide composite gel.
[0033] The multilayer nano-graphene oxide in this invention is commercially available, for example, it can be purchased from Shenzhen Liyou New Energy Technology Co., Ltd., model Graphene-510.
[0034] Preferably, the concentration of the graphene oxide dispersion is 5~20 mg / mL, and more preferably 8~10 mg / mL.
[0035] There are no special limitations on the above dispersion method; it can be performed by ultrasonication at 400-600W for 20-30 minutes.
[0036] Preferably, the mass of the graphene oxide is 20% to 50% of the total mass of the acrylamide, p-styrenesulfonic acid and N,N'-bis(acryloyl)cysteine, more preferably 45% to 50%.
[0037] Preferably, the mass concentration of the sodium hydroxide aqueous solution is 40% to 50%.
[0038] Preferably, the conditions for the first reaction include: a temperature of 40~50°C and a time of 1.5~2 hours.
[0039] Preferably, the initiator is 1% to 2% of the total mass of the acrylamide, p-styrenesulfonic acid and N,N'-bis(acryloyl)cysteine.
[0040] Preferably, the initiator is selected from at least one of ammonium persulfate, sodium persulfate, potassium persulfate, and azobisisobutyronitrile, with ammonium persulfate being the most preferred.
[0041] Preferably, the conditions for the second reaction include: a temperature of 40~50°C and a time of 1.5~2 hours.
[0042] Preferably, the conditions for the gelation reaction include standing at 40-50°C for 8-16 hours.
[0043] Preferably, the drying conditions include: a drying temperature of 80~90℃ and a drying time of 12~24 hours.
[0044] The above-mentioned pulverization method can be any method in the art, preferably pulverizing into graphene oxide composite gel with an average diameter of 80~200 micrometers.
[0045] Specifically, the preparation method of the graphene oxide composite gel includes: dispersing graphene oxide in water under ultrasonication at 400-600W for 20-30 minutes to obtain a graphene oxide dispersion with a concentration of 8-10 mg / mL; then adding acrylamide and p-styrene sulfonic acid and reacting at 40-50℃ for 1.5-2 hours; then adjusting the pH of the system to 7-8 using a 40%-50% sodium hydroxide aqueous solution; then sequentially adding N,N'-bis(acryloyl)cysteine and ammonium persulfate and reacting at 40-50℃ for 1.5-2 hours; finally, allowing it to stand at 40-50℃ for 8-1... The gel is formed in 6 hours, and then dried at 80~90℃ for 12~24 hours and pulverized into graphene oxide composite gel with an average particle size of 80~200 micrometers. The molar ratio of acrylamide, p-styrene sulfonic acid and N,N'-bis(acryloyl)cysteine is 1:(0.65~0.7):(0.2~0.25). The mass of graphene oxide is 45%~50% of the total mass of acrylamide, p-styrene sulfonic acid and N,N'-bis(acryloyl)cysteine. The mass of ammonium persulfate is 1%~2% of the total mass of acrylamide, p-styrene sulfonic acid and N,N'-bis(acryloyl)cysteine.
[0046] The second aspect of the present invention provides a method for preparing the modified admixture applicable to soft rock caving concrete as described in the first aspect of the present invention, the preparation method comprising: ball milling polyfatty acid modified graphene oxide and graphene oxide composite gel to obtain the modified admixture.
[0047] In this invention, ball milling enables polyfatty acid modified graphene oxide and graphene oxide composite gel to better form composite reinforcing units, thereby increasing the overall effect of the modified admixture in soft rock slag concrete.
[0048] Preferably, the ball milling method includes: placing polyfatty acid modified graphene oxide and graphene oxide composite gel in a planetary ball mill, setting the rotation speed to 350-400 rpm, and the total effective ball milling time to 2-3 hours.
[0049] When the modified admixture in this invention is used in soft rock slag concrete, the soft rock slag concrete generally includes cement, the above-mentioned modified admixture, soft rock slag, water, additives, etc., mixed and stirred according to the calculated mix proportion to achieve fluidity, plasticity, and hardening to form an artificial concrete material. For example, the preparation of soft rock slag concrete includes: accurately weighing cement (which can be 42.5 grade silicate cement), fly ash (which can be grade II fly ash), slag powder (which can be S95 grade granulated blast furnace slag powder), crushed soft rock slag coarse and fine aggregates, and modified admixtures according to the mix proportion; putting all dry components (cement, fly ash, slag powder, slag aggregates, and modified admixtures) into a mixer for dry mixing, and then adding water and a high-performance water-reducing agent (such as YK-PC polycarboxylate water-reducing agent) for wet mixing.
[0050] For example: Dry-mix 100 parts by weight of 42.5 grade silicate cement, 10-30 parts by weight of modified admixture, 8-15 parts by weight of grade II fly ash, 10-30 parts by weight of S95 grade granulated blast furnace slag powder, 180-300 parts by weight of coarse aggregate (manufactured sand processed from crushed tunnel slag, fineness modulus 3.42), and 200-350 parts by weight of fine aggregate (manufactured sand processed from crushed tunnel slag, fineness modulus 2.28). Then, add 30-80 parts by weight of water and 0.5-5 parts by weight of YK-PC polycarboxylate high-performance water-reducing agent in sequence and mix evenly to obtain concrete mix.
[0051] Compared with the prior art, the present invention has at least the following beneficial effects: The modified admixture, which combines polyfatty acid-modified graphene oxide and graphene oxide composite gel in an optimized ratio, can significantly improve the density of soft rock slag concrete when used in concrete, resulting in high compressive strength and excellent impermeability. It can also greatly improve the long-term durability of concrete and has excellent effects in resisting freeze-thaw cycles and chloride ion erosion, thus realizing the high-value-added resource utilization of low-quality soft rock slag. Detailed Implementation
[0052] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0053] In the following embodiments: The graphene oxide is a multilayer nano-graphene oxide with a Dv50 particle size of 30 micrometers, an average thickness of 5.2 nanometers, and an average number of 7 layers. It was purchased from Shenzhen Liyou New Energy Technology Co., Ltd., and the model number is Graphene-510.
[0054] Example 1 Preparation of polyfatty acid modified graphene oxide: (1) Graphene oxide was ultrasonically dispersed in N,N-dimethylformamide at 500W for 30 minutes to obtain a graphene oxide dispersion with a concentration of 1.5 mg / mL. (2) Thionyl chloride was added dropwise (completed over 30 minutes) to the graphene oxide dispersion and refluxed at 68°C for 16 hours. The resulting material was then filtered, the filter cake was washed five times with tetrahydrofuran, and then dried in a vacuum drying oven at 72°C for 12 hours to obtain the graphene oxide intermediate. The mass ratio of thionyl chloride to graphene oxide was 34:1. (3) Dissolve palmitic acid dimer in tetrahydrofuran to obtain a polyfatty acid solution with a concentration of 16 mg / mL, and disperse the graphene oxide intermediate in tetrahydrofuran under ultrasonication at 500 W for 50 minutes to obtain a graphene oxide intermediate dispersion with a concentration of 4.2 mg / mL. (4) The polyfatty acid solution was added dropwise (completed over 30 minutes) to the graphene oxide intermediate dispersion and refluxed at 64°C for 32 hours. The material obtained from the reflux reaction was filtered, and the filter cake was washed 5 times with anhydrous ethanol. Finally, it was dried in a vacuum drying oven at 45°C for 12 hours to obtain polyfatty acid modified graphene oxide. The mass ratio of palmitic acid dimer acid in the polyfatty acid solution to graphene oxide intermediate in the graphene oxide intermediate dispersion was 13.5:1.
[0055] Preparation of graphene oxide gel: A graphene oxide dispersion with a concentration of 8.6 mg / mL was prepared by ultrasonically dispersing graphene oxide in water at 500 W for 30 minutes. Acrylamide and p-styrene sulfonic acid were then added and reacted at 48 °C for 2 hours. The pH of the system was then adjusted to 7.6 using a 42% sodium hydroxide aqueous solution. N,N'-bis(acryloyl)cysteine and ammonium persulfate were then added sequentially and reacted at 48 °C for 2 hours. Finally, the mixture was allowed to stand at 48 °C for 12 hours to form a gel. The gel was then dried at 85 °C for 24 hours and pulverized into a graphene oxide composite gel with an average particle size of 120 μm. The molar ratio of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine was 1:0.68:0.23. The mass of graphene oxide was 48% of the total mass of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine. The mass of ammonium persulfate was 1.8% of the total mass of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine.
[0056] Preparation of modified admixtures: Polyfatty acid modified graphene oxide and graphene oxide composite gel with a mass ratio of 1:4.6 were placed in a planetary ball mill and ball milled at a speed of 380 rpm for a total effective ball milling time of 2.5 hours to obtain the modified additive.
[0057] Example 2 Preparation of polyfatty acid modified graphene oxide: (1) Graphene oxide was ultrasonically dispersed in N,N-dimethylformamide at 500W for 20-30 minutes to obtain a graphene oxide dispersion with a concentration of 2 mg / mL. (2) Thionyl chloride was added dropwise (completed over 30 minutes) to the graphene oxide dispersion and refluxed at 70°C for 12 hours. The resulting material was then filtered, and the filter cake was washed five times with tetrahydrofuran. The material was then dried in a vacuum drying oven at 72°C for 12 hours to obtain the graphene oxide intermediate. The mass ratio of thionyl chloride to graphene oxide was 40:1. (3) Dissolve palmitic acid dimer in tetrahydrofuran to obtain a polyfatty acid solution with a concentration of 18 mg / mL, and disperse the graphene oxide intermediate in tetrahydrofuran by ultrasonication at 500 W for 60 minutes to obtain a graphene oxide intermediate dispersion with a concentration of 3 mg / mL. (4) The polyfatty acid solution was added dropwise (completed over 30 minutes) to the graphene oxide intermediate dispersion and refluxed at 65°C for 30 hours. The material obtained from the reflux reaction was filtered, and the filter cake was washed 5 times with anhydrous ethanol. Finally, it was dried in a vacuum drying oven at 45°C for 12 hours to obtain polyfatty acid modified graphene oxide. The mass ratio of palmitic acid dimer acid in the polyfatty acid solution to graphene oxide intermediate in the graphene oxide intermediate dispersion was 15:1.
[0058] Preparation of graphene oxide gel: A graphene oxide dispersion with a concentration of 8 mg / mL was prepared by ultrasonically dispersing it in water at 500 W for 30 minutes. Acrylamide and p-styrene sulfonic acid were then added and reacted at 50 °C for 1.5 hours. The pH of the system was then adjusted to 7.8 using a 40% sodium hydroxide aqueous solution. N,N'-bis(acryloyl)cysteine and ammonium persulfate were added sequentially and reacted at 40 °C for 2 hours. Finally, the mixture was allowed to stand at 40 °C for 16 hours to form a gel. The gel was then dried at 85 °C for 24 hours and pulverized into a graphene oxide composite gel with an average particle size of 120 μm. The molar ratio of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine was 1:0.7:0.2. The mass of graphene oxide was 50% of the total mass of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine. The mass of ammonium persulfate was 2% of the total mass of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine.
[0059] Preparation of modified admixtures: Polyfatty acid modified graphene oxide and graphene oxide composite gel with a mass ratio of 1:5 were placed in a planetary ball mill and ball milled at a speed of 400 rpm for a total effective ball milling time of 2 hours to obtain the modified additive.
[0060] Example 3 The method according to Example 1 differs in that: In the preparation of the modified admixture, the mass ratio of polyfatty acid modified graphene oxide to graphene oxide composite gel is 1:5, and the modified admixture is finally prepared.
[0061] Comparative Example 1 The method according to Example 1 differs in that: In the preparation of graphene oxide gel, the molar ratio of acrylamide, p-styrenesulfonic acid and N,N'-bis(acryloyl)cysteine was 1:0.33:0.77.
[0062] Finally, graphene oxide gel and corresponding modified additives were prepared.
[0063] Comparative Example 2 The method according to Example 1 differs in that: In the preparation of graphene oxide gel, the molar ratio of acrylamide, p-styrenesulfonic acid and N,N'-bis(acryloyl)cysteine was 1:2.3:2.7.
[0064] Finally, graphene oxide gel and corresponding modified additives were prepared.
[0065] Comparative Example 3 The method according to Example 1 differs in that: Preparation of graphene oxide gel: A graphene oxide dispersion with a concentration of 8.6 mg / mL was prepared by ultrasonically dispersing graphene oxide in water at 500 W for 30 minutes. Acrylamide and p-styrene sulfonic acid were then added and reacted at 48 °C for 2 hours. The pH of the system was then adjusted to 7.6 using a 42% sodium hydroxide aqueous solution. Ammonium persulfate was then added and reacted at 48 °C for 2 hours. Finally, the mixture was allowed to stand at 48 °C for 12 hours to form a gel. The gel was then dried at 85 °C for 24 hours and pulverized into a graphene oxide composite gel with an average particle size of 120 μm. The molar ratio of acrylamide to p-styrene sulfonic acid was 1:0.68. The mass of graphene oxide was 48% of the total mass of acrylamide and p-styrene sulfonic acid, and the mass of ammonium persulfate was 1.8% of the total mass of acrylamide and p-styrene sulfonic acid.
[0066] Finally, graphene oxide gel and corresponding modified additives were prepared.
[0067] Comparative Example 4 The method according to Example 1 differs in that: In the preparation of graphene oxide gel, N,N'-bis(acryloyl)cystamine was replaced with N,N'-methylenebisacrylamide.
[0068] Finally, graphene oxide gel and corresponding modified additives were prepared.
[0069] Comparative Example 5 The method according to Example 1 differs in that: The polyfatty acid modified graphene oxide was replaced with fatty acid modified graphene oxide; the palmitic acid dimer acid in the preparation of polyfatty acid modified graphene oxide in Example 1 was replaced with palmitic acid.
[0070] The modified additive was finally prepared.
[0071] Comparative Example 6 The method according to Example 1 differs in that: In the preparation of the modified admixture, the mass ratio of polyfatty acid modified graphene oxide to graphene oxide composite gel was 4.6:1, and the modified admixture was finally prepared.
[0072] Comparative Example 7 The graphene oxide composite gel from Example 1 was used directly as a modifying additive.
[0073] Performance testing Test samples were prepared using the modified additives from Examples 1-3 and Comparative Examples 1-7, respectively, and the corresponding performance tests were performed. Preparation of test samples: 328 kg of 42.5 grade silicate cement, 60 kg of modified admixture, 45 kg of grade II fly ash, 50 kg of S95 grade granulated blast furnace slag powder, 750 kg of coarse aggregate (manufactured sand processed from crushed tunnel slag with a fineness modulus of 3.42), and 800 kg of fine aggregate (manufactured sand processed from crushed tunnel slag with a fineness modulus of 2.28) were dry-mixed evenly. Then, 153 kg of water and 5 kg of YK-PC polycarboxylate high-performance water-reducing agent were added in sequence and mixed evenly to obtain concrete mixture.
[0074] The concrete mixture was poured into a concrete mold (10cm×10cm×10cm) and vibrated. The surface of the specimen was covered with plastic wrap to form concrete specimens. After standing for one day, the mold was removed, and the specimens were placed in a standard curing chamber for 28 days to form concrete test blocks. The compressive strength and flexural strength of the specimens were tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Simultaneously, referring to the rapid freezing method in GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the mass loss rate of the specimens was tested after 300 freeze-thaw cycles. Referring to Chapter 7 of GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the chloride ion diffusion coefficient of the specimens was tested; a smaller value indicates higher density and better durability.
[0075] Concrete specimens were prepared using the "water penetration height method" in GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The concrete specimens were installed in a permeability meter for permeability testing. The water pressure was kept constant between 1.15-1.25 MPa for 24 hours. After 24 hours, the specimen was split and the water mark height was measured. The test was repeated 5 times and the average water mark height was calculated. The higher the water penetration height, the worse the water penetration resistance of the specimen.
[0076] The test results are shown in Table 1.
[0077] Table 1 Performance Test Results
[0078] As can be seen from the above performance test results, the modified admixtures in Examples 1-3 can significantly improve the density of concrete when used in soft rock caving, enabling it to obtain higher compressive strength and excellent impermeability. They can also greatly improve the long-term durability of concrete and have excellent effects in resisting freeze-thaw cycles and chloride ion erosion.
[0079] The comparative examples, lacking the necessary technical solutions, performed significantly worse than the exemplary examples in relevant performance tests. In Comparative Examples 1-2, the proportions of acrylamide, p-styrene sulfonic acid, and N,N'-bis(acryloyl)cysteine segments in the graphene oxide composite gel were outside the preferred range. This resulted in a significant decrease in the mechanical strength of the final concrete and an increase in structural defects when the modified admixture was used in soft rock caving debris, leading to poorer impermeability. In Comparative Example 3, the graphene oxide composite gel lacked N,N'-bis(acryloyl)cysteine segments, resulting in a decrease in the overall performance of the final concrete when the modified admixture was used in soft rock caving debris, particularly a severe reduction in impermeability and durability. In Comparative Example 4, the N,N'-bis(acryloyl)cysteine segments in the graphene oxide composite gel were replaced with... The N,N'-methylenebisacrylamide segment reduces the flexural strength and impermeability of concrete when the modified admixture is used in soft rock caving debris to some extent. In Comparative Example 5, replacing the polyfatty acid (palmitic acid dimer) with a monofatty acid worsens the strengthening and impermeability effects of the modified admixture when used in soft rock caving debris. In Comparative Example 6, the mass ratio of polyfatty acid-modified graphene oxide to graphene oxide composite gel is not within the optimal range, resulting in a comprehensive decrease in the mechanical properties and impermeability of concrete when the modified admixture is used in soft rock caving debris. In Comparative Example 7, the use of a single graphene oxide composite gel as the modified admixture significantly reduces the impermeability and mechanical strengthening effect of the concrete, further illustrating the synergistic effect of polyfatty acid-modified graphene oxide and graphene oxide composite gel.
[0080] The above experimental results further demonstrate the importance of the technical solution defined in this invention to its technical effect.
[0081] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A modified admixture suitable for soft rock caving concrete, characterized in that, The modified additives include polyfatty acid modified graphene oxide and graphene oxide composite gel.
2. The modified admixture for soft rock caving concrete according to claim 1, characterized in that, The mass ratio of the polyfatty acid modified graphene oxide to the graphene oxide composite gel is 1:(1~10).
3. The modified admixture for soft rock caving concrete according to claim 1, characterized in that, The polyfatty acid in the polyfatty acid modified graphene oxide is selected from at least one of octadecyl unsaturated fatty acid dimers, linoleic acid dimers, and palmitic acid dimers.
4. The modified admixture for soft rock caving concrete according to claim 3, characterized in that, The preparation method of the polyfatty acid modified graphene oxide includes: (1) Graphene oxide was dispersed in N,N-dimethylformamide to obtain a graphene oxide dispersion; (2) Thionyl chloride was added dropwise to the graphene oxide dispersion for reaction, and then filtered, washed and dried to obtain the graphene oxide intermediate. (3) Polyfatty acid is dissolved in tetrahydrofuran to obtain a polyfatty acid solution, and graphene oxide intermediate is dispersed in tetrahydrofuran to obtain a graphene oxide intermediate dispersion. (4) The polyfatty acid solution was added dropwise to the graphene oxide intermediate dispersion for reflux reaction, followed by filtration, washing and drying to obtain polyfatty acid modified graphene oxide.
5. The modified admixture for soft rock caving concrete according to claim 4, characterized in that, The graphene oxide is nano-graphene oxide, and the nano-graphene oxide has a multilayer structure; in step (1), the concentration of the graphene oxide dispersion is 1~2 mg / mL; in step (2), the mass ratio of thionyl chloride to graphene oxide is (30~40):1; in step (2), the reaction conditions include: reflux reaction at 65~75℃ for 12~30 hours; in step (2), the thionyl chloride is added dropwise for 20~30 minutes.
6. The modified admixture for soft rock caving concrete according to claim 4, characterized in that, In step (3), the concentration of the polyfatty acid solution is 10~20 mg / mL; in step (3), the concentration of the graphene oxide intermediate dispersion is 1~10 mg / mL; in step (4), the mass ratio of the polyfatty acid in the polyfatty acid solution to the graphene oxide intermediate in the graphene oxide intermediate dispersion is (10~20):1; in step (4), the reflux reaction conditions include: temperature 60~65℃, time 30~40 hours.
7. The modified admixture for soft rock caving concrete according to claim 1, characterized in that, The modified segments in the graphene oxide composite gel include acrylamide segments, p-styrene sulfonic acid segments, and N,N'-bis(acryloyl)cysteine segments; the molar ratio of the acrylamide segments, p-styrene sulfonic acid segments, and N,N'-bis(acryloyl)cysteine segments is 1:(0.5~0.8):(0.15~0.3).
8. The modified admixture for soft rock caving concrete according to any one of claims 1-7, characterized in that, A graphene oxide dispersion was prepared by dispersing graphene oxide in water. Acrylamide and p-styrene sulfonic acid were then added to carry out the first reaction. The pH of the system was then adjusted to 7-8 using sodium hydroxide aqueous solution. N,N'-bis(acryloyl)cysteine and an initiator were added sequentially to carry out the second reaction. Finally, a gelation reaction was carried out, followed by drying and pulverization to obtain a graphene oxide composite gel.
9. The modified admixture for soft rock caving concrete according to claim 8, characterized in that, The mass of the graphene oxide is 20% to 50% of the total mass of the acrylamide, p-styrenesulfonic acid, and N,N'-bis(acryloyl)cysteine; the conditions for the first reaction include a temperature of 40 to 50°C and a time of 1.5 to 2 hours; the conditions for the second reaction include a temperature of 40 to 50°C and a time of 1.5 to 2 hours; the conditions for the gelation reaction include standing at 40 to 50°C for 8 to 16 hours.
10. A method for preparing a modified admixture suitable for soft rock caving concrete as described in any one of claims 1 to 9, characterized in that, The preparation method includes: ball milling polyfatty acid modified graphene oxide and graphene oxide composite gel to obtain modified additives.